Radiation

Q. Give three applications of convection of heat .

Q.

How does heat get transferred in vacuum?

Q.

The heat from the Sun reaches Earth through conduction.

1. True

2. False

Q. A thermos flask is designed to prevent the contents of the flask from losing heat. Which of the following statements concerning the design of thermos flasks is incorrect?

1. The flask is designed to prevent heat loss by conduction, convection and radiation.
2. The inner glass walls are silver coated to reduce emitted radiation.
3. The vacuum between the glass walls prevents heat loss by conduction and convection.
4. The insulated cap helps enhance heat flow by radiation.

Q.

Which of the following modes of heat transfer does not require any medium for transfer of heat?

1. Convection

2. Radiation

3. Conduction

4. Conduction and convection

Q. Explain Why the space between the two walls in a thermos flask is vacuum?

Q.

What is the fastest and the slowest mode of heat transfer? [2 MARKS]

Q. Why is it advisable to wear light coloured clothes during summer?

1. They are cheaper.
2. They absorb less heat.
3. They absorb more heat.
4. They are more beautiful to the eyes.

Q. No medium is required for transfer of heat by ________.

1. Conduction
2. Convection
3. Radiation
4. Both b and c

Q. Explain the design of a thermos flask.

Q.

What is the difference between refrigeration and freezing?

Q.

Why cooking vessels are colored black at the bottom?

Q.

Black surfaces are poor absorbers of heat radiation.

1. True
2. False

Q.

No medium is required for transfer of heat by

1. conduction

2. convection

3. radiation

4. both b and c

Q.

Define: Radiant heat

Q. Heat transfer through waves is called:

1. Conduction
2. Convection
3. Radiation
4. Reflection

Q. On a sunny day, it is cool in the shade below a tree but not away from it because:

1. None of these

2. Air trapped between leaves is a good conductor of heat.

3. Heat radiation travel in straight line.

4. The tree produces cold air

Q.

Which of the following modes of heat transfer does not require any particle for transfer of heat energy?

1. Convection

2. Radiation

3. Conduction

4. None of the above

Q.

At a campsite, there are tents of two shades – one made with black fabric and the other with white fabric. Which one will you prefer for resting on a hot summer afternoon? Give a reason for your choice. Would you like to prefer the same tent during winter?

Q. Statement 1: All hot bodies radiate heat.
Statement 2: Medium is required for transfer of heat by the process of radiation.

1. Statement 1 is true, statement 2 is false
2. Statement 1 is false, statement 2 is true
3. Both statements are true
4. Both statements are false

Q. The underside of cooking utensils is blackened but its side are kept polished. Why?

Q.

Which of the following mode does not require medium for heat transfer?

1. Conduction

2. Convection

3. Radiation

4. Can’t be said

Q. In the following figure, assuming the two thermometers have the same initial reading, which of the two would record a higher rise in temperature, when placed near the candle as shown?

1. A
2. Both A and B would have the same rise in temperature.
3. The mercury level in A and B would not rise at all.
4. B

Q.

For the effective radiation of heat by an electric room heater, which of the following needs to be done?

1. Make it unshiny.

2. Paint it green

3. Paint it black

4. Polish it to shine.

Q.

The heat radiation travels in vacuum with speed

1. more than speed of light

2. equal to speed of light

3. equal to infinity

4. less than speed of light

Q.

Thermal radiation can travel even through __________________.

Q.

Define the following: radiant energy

Q. If we heat an entire closed room by using a heater, which of the following modes of heat transfer is dominant in this process?

1. Conduction
2. Convection
   
3. Convection and radiation
   
4. Conduction, convection, and radiation

Q.

The heat energy gets transferred from sun to earth by process of ___

Q.

Which part of a thermos flask prevents loss of heat?

1. Double glass walls

2. Shiny, silvery wall

3. Vacuum

4. Cork stopper